Is salinity the main ecologic factor that shapes the distribution of two endemic Mediterranean plant species of the genus Gypsophila?

The final publication is available at Springer via http://dx.doi.org/10.1007/s11104-014-2218-2Aims Responses to salt stress of two Gypsophila species that share territory, but with different ecological optima and distribution ranges, were analysed. G. struthium is a regionally dominant Iberian endemic gypsophyte, whereas G. tomentosa is a narrow endemic reported as halophyte. Theworking hypothesis is that salt tolerance shapes the presence of these species in their specific habitats. Methods Taking a multidisciplinary approach, we assessed the soil characteristics and vegetation structure at the sampling site, seed germination and seedling development, growth and flowering, synthesis of proline and cation accumulation under artificial conditions of increasing salt stress and effect of PEG on germination and seedling development. Results Soil salinity was low at the all sampling points where the two species grow, but moisture was higher in the area of G. tomentosa. Differences were found in the species salt and drought tolerance. The different parameters tested did not show a clear pattern indicating the main role of salt tolerance in plant distribution. Conclusions G. tomentosa cannot be considered a true halophyte as previously reported because it is unable to complete its life cycle under salinity. The presence of G. tomentosa in habitats bordering salt marshes is a strategy to avoid plant competition and extreme water stressSoriano, P.; Moruno Manchón, JF.; Boscaiu Neagu, MT.; Vicente Meana, Ó.; Hurtado, A.; Llinares Palacios, JV.; Estrelles, E. (2014). Is salinity the main ecologic factor that shapes the distribution of two endemic Mediterranean plant species of the genus Gypsophila?. Plant and Soil. 384(1-2):363-379. doi:10.1007/s11104-014-2218-2S3633793841-2Alonso MA (1996) Flora y vegetación del Valle de Villena (Alicante). 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Opportunistic Germination Behaviour of Gypsophila (Caryophyllaceae) in Two Priority Habitats from Semi-arid Mediterranean Steppes

Gypsophila tomentosa and G. struthium are closely related species, characteristic of two European priority habitats, salt and gypsum inland steppes, respectively. Germination strategies of the two taxa were investigated in plants from two nearby populations, growing under the same climatic conditions but on different types of soil, and belonging to different plant communities. Their germination patterns were studied at five constant temperatures in darkness: 5oC, 10oC, 15oC, 20oC and 25oC, and the base temperature and the thermal time requirement were calculated. As the distribution area of both species is subjected to a Mediterranean continental climate with significant differences between day and night, the possible preferences for an alternating temperature regime (25/10oC) were contrasted, as well as the influence of cold stratification and freezing. The effects on seed germination of light at constant 20oC and a 12/12 h photoperiod were also compared in the two species. The main conclusions of the work are the similarity of behaviour of both species, with an absence of seed dormancy, their opportunistic germination strategy, and water availability as the principal limitation to seed germination and plant establishment. The base temperature and thermal time indicate higher competitiveness of G. struthium at low temperatures, but seed germination of G. tomentosa is the most efficient at temperatures higher than 13.3oC. Optimal temperature and illumination conditions for nursery propagation depend on the species. The high viability of seeds observed after freezing prove the orthodox character of these seeds, providing additional information for long term seed conservation procedures

SPHK1/sphingosine kinase 1-mediated autophagy differs between neurons and SH-SY5Y neuroblastoma cells

Although implicated in neurodegeneration, autophagy has been characterized mostly in yeast and mammalian non-neuronal cells. In a recent study, we sought to determine if SPHK1 (sphingosine kinase 1), implicated previously in macroautophagy/autophagy in cancer cells, regulates autophagy in neurons. SPHK1 synthesizes sphingosine-1-phosphate (S1P), a bioactive lipid involved in cell survival. In our study, we discovered that, when neuronal autophagy is pharmacologically stimulated, SPHK1 relocalizes to the endocytic and autophagic organelles. Interestingly, in non-neuronal cells stimulated with growth factors, SPHK1 translocates to the plasma membrane, where it phosphorylates sphingosine to produce S1P. Whether SPHK1 also binds to the endocytic and autophagic organelles in non-neuronal cells upon induction of autophagy has not been demonstrated. Here, we determined if the effect in neurons is operant in the SH-SY5Y neuroblastoma cell line. In both non-differentiated and differentiated SH-SY5Y cells, a short incubation of cells in amino acid-free medium stimulated the formation of SPHK1-positive puncta, as in neurons. We also found that, unlike neurons in which these puncta represent endosomes, autophagosomes, and amphisomes, in SH-SY5Y cells SPHK1 is bound only to the endosomes. In addition, a dominant negative form of SPHK1 was very toxic to SH-SY5Y cells, but cultured primary cortical neurons tolerated it significantly better. These results suggest that autophagy in neurons is regulated by mechanisms that differ, at least in part, from those in SH-SY5Y cells

Cytoplasmic sphingosine-1-phosphate pathway modulates neuronal autophagy

Autophagy is an important homeostatic mechanism that eliminates long-lived proteins, protein aggregates and damaged organelles. Its dysregulation is involved in many neurodegenerative disorders. Autophagy is therefore a promising target for blunting neurodegeneration. We searched for novel autophagic pathways in primary neurons and identified the cytosolic sphingosine-1-phosphate (S1P) pathway as a regulator of neuronal autophagy. S1P, a bioactive lipid generated by sphingosine kinase 1 (SK1) in the cytoplasm, is implicated in cell survival. We found that SK1 enhances flux through autophagy and that S1P-metabolizing enzymes decrease this flux. When autophagy is stimulated, SK1 relocalizes to endosomes/autophagosomes in neurons. Expression of a dominant-negative form of SK1 inhibits autophagosome synthesis. In a neuron model of Huntington's disease, pharmacologically inhibiting S1P-lyase protected neurons from mutant huntingtin-induced neurotoxicity. These results identify the S1P pathway as a novel regulator of neuronal autophagy and provide a new target for developing therapies for neurodegenerative disorders

Levetiracetam mitigates doxorubicin-induced DNA and synaptic damage in neurons

Neurotoxicity may occur in cancer patients and survivors during or after chemotherapy. Cognitive deficits associated with neurotoxicity can be subtle or disabling and frequently include disturbances in memory, attention, executive function and processing speed. Searching for pathways altered by anti-cancer treatments in cultured primary neurons, we discovered that doxorubicin, a commonly used anti-neoplastic drug, significantly decreased neuronal survival. The drug promoted the formation of DNA double-strand breaks in primary neurons and reduced synaptic and neurite density. Pretreatment of neurons with levetiracetam, an FDA-approved anti-epileptic drug, enhanced survival of chemotherapy drug-treated neurons, reduced doxorubicin-induced formation of DNA double-strand breaks, and mitigated synaptic and neurite loss. Thus, levetiracetam might be part of a valuable new approach for mitigating synaptic damage and, perhaps, for treating cognitive disturbances in cancer patients and survivors

Follow-up of a simple method for aortic valve reconstruction with fixed pericardium in children.

In 2013, we published a simple method for aortic valve reconstruction in children using fixed pericardium in this journal. This was not expected to be a durable solution but a temporizing measure in the absence of other solutions, in order to buy time for growth that would allow subsequent prosthetic valve insertion. As such, this was implemented in 3 patients with excellent immediate results, as reported in our original publication. We are now writing to provide longer term information. In 2 cases, a newborn and a 12-year-old boy, the valve calcified heavily at 4 years' follow-up. By then, the valvar annulus had grown sufficiently to accept a prosthetic valve in both cases. In these 2 cases, the material used for valve reconstruction was autologous pericardium fixed in 0.6% gluteraldehyde. In the third patient, a 3-year-old girl, the valve failed by dehiscence of the suture line 6 months following surgery. In this case, fixed bovine pericardium had been used, which is more rigid than autologous pericardium, thus possibly explaining the dehiscence. However, the pericardial patch was not calcified. Thus, the described method lived up to our expectation of buying time for growth for later insertion of a prosthetic valve in 2 of the 3 cases